A Scala port of miniKanren

Based on https://github.com/michel-slm/minikanren-scala

Please check the documentation in docs/presentation.rst for details.

You can also check the (basic) tutorial of miniKanren with this Scala syntax, using the following command (in the root project's sbt shell):

> miniKanrenExamplesJVM/tut

snd check the output markdown file in examples/jvm/target/scala-2.12/tut

Using REPL with SBT:

> miniKanrenExamplesJVM/console

...

scala> time(run(1, x)(solve_puzzle(x)))
res0: (Long, Any) = (10044,List(List(9567, 1085, 10652)))

Interpretation of the result: took 10044 milliseconds to solve the problem, a result is

 SEND   9567
+MORE  +1085
-----  -----
MONEY  10652

Another example (palindromes with six-digit numbers that are the product of two three-digit numbers), this time with maprun as it is much faster:

time(maprun(1, x)(palprod_o(x)))
100001
101101
res1: (Long, Any) = (40837,List((1,(1,(1,(0,(0,(1,(1,(1,(1,(1,(0,(0,(0,(1,List()))))))))))))))))